diff --git a/src/mos6502.arith.c b/src/mos6502.arith.c
index eb75028..3accbd9 100644
--- a/src/mos6502.arith.c
+++ b/src/mos6502.arith.c
@@ -17,6 +17,8 @@ DEFINE_INST(adc)
 {
     CARRY_BIT();
     cpu->A += oper + carry;
+
+    mos6502_modify_status(cpu, NEGATIVE | OVERFLOW | CARRY | ZERO, cpu->A);
 }
 
 /*
@@ -59,6 +61,7 @@ DEFINE_INST(dec)
 {
     if (cpu->last_addr) {
         vm_segment_set(cpu->memory, cpu->last_addr, oper - 1);
+        mos6502_modify_status(cpu, NEGATIVE | ZERO, oper - 1);
     }
 }
 
@@ -68,6 +71,7 @@ DEFINE_INST(dec)
 DEFINE_INST(dex)
 {
     cpu->X--;
+    mos6502_modify_status(cpu, NEGATIVE | ZERO, cpu->X);
 }
 
 /*
@@ -76,6 +80,7 @@ DEFINE_INST(dex)
 DEFINE_INST(dey)
 {
     cpu->Y--;
+    mos6502_modify_status(cpu, NEGATIVE | ZERO, cpu->Y);
 }
 
 /*
@@ -87,6 +92,7 @@ DEFINE_INST(inc)
 {
     if (cpu->last_addr) {
         vm_segment_set(cpu->memory, cpu->last_addr, oper + 1);
+        mos6502_modify_status(cpu, NEGATIVE | ZERO, oper + 1);
     }
 }
 
@@ -96,6 +102,7 @@ DEFINE_INST(inc)
 DEFINE_INST(inx)
 {
     cpu->X++;
+    mos6502_modify_status(cpu, NEGATIVE | ZERO, cpu->X);
 }
 
 /*
@@ -104,6 +111,7 @@ DEFINE_INST(inx)
 DEFINE_INST(iny)
 {
     cpu->Y++;
+    mos6502_modify_status(cpu, NEGATIVE | ZERO, cpu->Y);
 }
 
 /*
@@ -116,4 +124,6 @@ DEFINE_INST(sbc)
 {
     CARRY_BIT();
     cpu->A = cpu->A - oper - carry;
+
+    mos6502_modify_status(cpu, NEGATIVE | OVERFLOW | CARRY | ZERO, cpu->A);
 }
diff --git a/src/mos6502.bits.c b/src/mos6502.bits.c
index 2e271ec..5b78e59 100644
--- a/src/mos6502.bits.c
+++ b/src/mos6502.bits.c
@@ -15,6 +15,7 @@
 DEFINE_INST(and)
 {
     cpu->A &= oper;
+    mos6502_modify_status(cpu, NEGATIVE | ZERO, cpu->A);
 }
 
 /*
@@ -42,6 +43,8 @@ DEFINE_INST(asl)
     } else {
         cpu->A = oper;
     }
+
+    mos6502_modify_status(cpu, NEGATIVE | CARRY | ZERO, oper);
 }
 
 /*
@@ -75,6 +78,7 @@ DEFINE_INST(bit)
 DEFINE_INST(eor)
 {
     cpu->A ^= oper;
+    mos6502_modify_status(cpu, NEGATIVE | ZERO, cpu->A);
 }
 
 /*
@@ -98,6 +102,9 @@ DEFINE_INST(lsr)
     } else {
         cpu->A = oper;
     }
+
+    // NEGATIVE is intentionally not included here.
+    mos6502_modify_status(cpu, CARRY | ZERO, oper);
 }
 
 /*
@@ -107,6 +114,7 @@ DEFINE_INST(lsr)
 DEFINE_INST(ora)
 {
     cpu->A |= oper;
+    mos6502_modify_status(cpu, NEGATIVE | ZERO, cpu->A);
 }
 
 /*
@@ -133,6 +141,8 @@ DEFINE_INST(rol)
     } else {
         cpu->A = oper;
     }
+
+    mos6502_modify_status(cpu, NEGATIVE | CARRY | ZERO, oper);
 }
 
 /*
@@ -158,4 +168,6 @@ DEFINE_INST(ror)
     } else {
         cpu->A = oper;
     }
+
+    mos6502_modify_status(cpu, NEGATIVE | CARRY | ZERO, oper);
 }
diff --git a/src/mos6502.loadstor.c b/src/mos6502.loadstor.c
index 14cefa4..6b13615 100644
--- a/src/mos6502.loadstor.c
+++ b/src/mos6502.loadstor.c
@@ -58,6 +58,7 @@ DEFINE_INST(php)
 DEFINE_INST(pla)
 {
     cpu->A = mos6502_pop_stack(cpu);
+    mos6502_modify_status(cpu, NEGATIVE | ZERO, cpu->A);
 }
 
 /*